Electro chemical machining (ECM) is a non-mechanical process for removing metal at an atomic level in an electrolytic cell. ECM is useful for machining hard, high strength, wear resistance metals that are difficult and expensive to shape using traditional methods. In addition, ECM is also useful to machine irregular shapes such as dies and molds which do not respond well to traditional machining methods.
The electrolytic cell in an ECM process consists of a tool electrode (cathode) and a work piece electrode (anode) that are separated by an interelectrode gap (IEG) through which an electrolytic solution (e.g. NaCl or NaO3) flows. In conventional ECM processes, the tool electrode is advanced towards the work piece electrode while an electric current passes through the electrolyte flowing through the IEG. This causes dissolution of the surface metal ions from the work piece into the electrolyte solution. Over time, accumulation of waste material, heat and exhaustion of the electrolytes in the IEG leads to unfavorable kinetics and reaction stoichiometry in the electrolytic cell. To remedy this, the electrolytic solution is flowed through the cell to remove the remove waste product and heat away from the IEG while supplying unreactive ions to maintain the electrically conductive path.
Additionally, a variety of technologies may be incorporated to improve the ECM process. One such method is to vary the current through the IEG. Pulsed ECM (PECM) processes employ a pulsed direct current (DC) electric field across the IEG to improve surface finish.
Ultrasonic actuation of the tool or work piece may also be incorporated to improve the ECM process. By speeding the metal hydroxide byproduct out the inter-electrode gap through mixing action which helps overcome the usual mass transport limitations the material removal rate and current efficiency of the process is improved. Additionally, cavitation from ultrasonic motion can inhibit the formation of the passivation layer which will increase the material removal rate. However, ultrasonic technology is typically viewed as a bulk treatment for an electrochemical reaction adding agitation or cavitation to a fluid involved in the chemical reaction.
Magnetic fields introduced in the electrochemical cell improve the conditions within the cell as well. When augmenting electrochemical cells, magnetic fields are typically generated from permanent magnets with changes in the magnetic field created using rotary motion of the magnets or work piece. When electromagnets are employed they typically function using direct current (DC) or at very low frequency alternating current (AC).
While it is currently known to combine two or more of these technologies to further improve the machining process, these efforts have primarily been focused on combining the individual effects without regard for any synergistic effects which may be realized. Accordingly, there is a need for an improved system and method for electrochemical machining.